Zoom lens system, imaging apparatus, and camera

ABSTRACT

A zoom lens system according to the disclosure, in order from an object side to an image side, includes a first lens group with positive optical power, a second lens group with negative optical power, and a subsequent lens group composed of at least three lens groups. During zooming operation, the first lens group moves along the optical axis and the second lens group does not move. The second lens group has an aperture stop. The second lens group satisfies following condition (1), 
       −9.0≦fG1/fG2≦−2.0   (1)
         where   fG1 is the focal length of the first lens group, and   fG2 is the focal length of the second lens group.

BACKGROUND

1. Technical Field

The present disclosure relates to a ZOOM lens system that is compact and has a high optical performance across the entire zoom area in spite of the large diameter, and to an imaging apparatus and a camera that include the zoom lens system.

2. Description of the Related Art

Patent literature 1 discloses a zoom optical system configured so that its imaging element moves in the optical axis direction at least during zooming for higher magnification and a smaller size.

CITATION LIST Patent Literature

PTL 1 Japanese PatentUnexamined Publication No. 1111-202201

SUMMARY

An object of the present disclosure is to provide a zoom lens system that is compact and has a high optical performance across the entire zoom area in spite of the high magnification, and an imaging apparatus and a camera that include the zoom lens system.

A zoom lens system according to the disclosure, in order from an object side to an image side, includes a first lens group with positive optical power, a second lens group with negative optical power, and a subsequent lens group composed of at least three lens groups.

During zooming operation, the first leas group moves along the optical axis and the second lens group does not move.

The second lens group has an aperture stop.

The second lens group satisfies following condition (1),

−9.0≦fG1/fG2≦−2.0   (1)

where

fG1 is the focal length of the first lens group, and

fG2 is the focal length of the second lens group.

The disclosure provides a zoom lens system that is compact and has a high optical performance across the entire zoom area in spite of the high magnification, and an imaging apparatus and a camera that include the zoom lens system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lens layout diagram of a zoom lens system according to the first embodiment (numerical practical example 1), showing an infinity focusing state.

FIG. 2 is a longitudinal aberration diagram of the zoom lens system according to the first embodiment, in an infinity focusing state.

FIG. 3 is a lateral aberration diagram of the zoom lens system according to the first embodiment, at the telephoto end in a basic state (image blur correction is not being performed) and in an image blur correction state.

FIG. 4 is a lens layout diagram of a zoom lens system according to the second embodiment (numerical practical example 2), showing an infinity focusing state.

FIG. 5 is a longitudinal aberration diagram of the zoom lens system according to the second embodiment, in an infinity focusing state.

FIG. 6 is a lateral aberration diagram of the zoom lens system according to the second embodiment, at the telephoto end in a basic state (image blur correction is not being performed) and in an image blur correction state.

FIG. 7 is a lens layout diagram of a zoom lens system according to the third embodiment (numerical practical example 3), showing an infinity focusing state.

FIG. 8 is a longitudinal aberration diagram of the zoom lens system according to the third embodiment, in an infinity focusing state.

FIG. 9 is a lateral aberration diagram of the zoom lens system according to the third embodiment, at the telephoto end in a basic state (image blur correction is not being performed) and in an image blur correction state.

FIG. 10 is an outline block diagram of an imaging apparatus to which the zoom lens system according to the first embodiment has been applied.

FIG. 11 is an outline block diagram of a camera to which the zoom lens system according to the first embodiment has been applied.

DETAILED DESCRIPTION

Hereinafter, a detailed description is made of some embodiments with reference to the related drawings as appropriate. However, a detailed description more than necessary may be omitted, such as a description of a well-known item and a duplicate description for a substantially identical component, to avoid an unnecessarily redundant description and to allow those skilled in the art to easily understand the following description.

Note that the applicant provides accompanying drawings and the following description for those skilled in the art to well understand the disclosure and does not intend to limit the subjects described in the claims by the drawings and the description.

First through Third Exemplary Embodiments

FIGS. 1, 4, and 7 are layout diagrams of the zoom lens systems according to the first through third embodiments, each illustrating a zoom lens system in an infinity focusing state.

In FIGS. 1, 4, and 7, part (a) shows a lens configuration of the wide-angle end (a state of the shortest focal length: fW); part (b), the intermediate position (a state of the intermediate focal length: fM=√(fW*fT)); and part (c), the telephoto end (a state of the longest focal length: fT). In parts (a) through (c), one aspect ratio agrees with another.

In FIGS. 1, 4, and. 7, zigzag arrows between parts (a) and (b) are straight lines connecting the positions of the lens groups in a state of the wide-angle end, intermediate position, and telephoto end, in sequence from the top. The parts between the wide-angle end and the intermediate position, and between the intermediate position and the telephoto end are simply connected by straight lines, which is different from actual movement of each lens group.

Further, in FIGS. 1, 4, and 7, the arrows on the lens groups indicate focusing from an infinity focusing state to a proximity focusing state. In FIGS. 1, 4, and 7, each mark of the lens groups is inscribed below each lens group in part (a), and thus arrows indicating focusing are inscribed below each mark of the lens groups for convenience. However, a direction in which each lens group moves for focusing in each zooming state is concretely described later for each embodiment.

In FIGS. 1, 4, and 7, an asterisk (*) inscribed on a specific surface represents the surface is aspheric. In FIGS. 1, 4, and 7, a symbol (+) and a symbol (−) affixed to each mark of the lens groups correspond to the sign of the optical power of each lens group. In FIGS. 1, 4, and 7, the straight line at the rightmost indicates the position of image surface S (the surface of the imaging element facing an object)

First Exemplary Embodiment

FIG. 1 illustrates a zoom lens system according to the first exemplary embodiment.

The zoom lens system is composed of first lens group G-1 with positive optical power, second lens group G2 with negative optical power, third lens group G3 with positive optical power, fourth lens group G4 with negative optical power, fifth lens group G5 with negative optical power, and parallel plain plate P, in this order in the direction from an object to the image. Third lens group G3, fourth lens group G4, and fifth lens group G5 compose the subsequent lens group.

First lens group G1 is composed of first lens element L1 with negative optical power, second lens element L2 with positive optical power, and third lens element L3 with positive optical power, in this order in the direction from an object to the image.

Second lens group G2 is composed of fourth lens element L4 with positive optical power, fifth lens element L5 with negative optical power, aperture stop A, sixth lens element L6 with negative optical power, seventh lens element L7 with positive optical power, eighth lens element L8 with positive optical power, and ninth lens element L9 with negative optical power, in this order in the direction from an object to the image. Fourth lens element L4 and fifth lens element L5 are bonded together with a bonding material for example to form a cemented lens, and so are sixth lens element L6 and seventh lens element L7, and eighth lens element L8 and ninth lens element L9.

Third lens group G3 is composed of tenth lens element L10 with positive optical power, eleventh lens element L11 with positive optical power, twelfth lens element L12 with negative optical power, thirteenth lens element L13 with negative optical power, fourteenth lens element L14 with positive optical power, fifteenth lens element L15 with positive optical power, sixteenth lens element L16 with positive optical power, and seventeenth lens element L17 with negative optical power, in this order in the direction from an object to the image. Eleventh lens element L11 and twelfth lens element L12 are bonded together with a bonding material for example to form a cemented lens, and so are thirteenth lens element L13 and fourteenth lens element L14, and sixteenth lens element L16 and seventeenth lens element L17.

Fourth lens group G4 is a single lens and is composed of eighteenth lens element L18 with negative optical power.

Fifth lens group G5 is composed of nineteenth lens element L19 with negative optical power and twentieth lens element L20 with positive optical power, in this order in the direction from an object to the image. Nineteenth lens element L19 and twentieth lens element L20 are bonded together with a bonding material for example to form a cemented lens.

Each lens element is described.

The lens elements in first lens group G1 are described. First lens element L1 is a meniscus lens having a convex surface facing an object. Second lens element L2 is a meniscus lens having a convex surface facing an object. Third lens element L3 is a meniscus lens having a convex surface facing an object.

The lens elements in second lens group G2 are described. Fourth lens element L4 is a biconvex lens. Fifth lens element L5 is a biconcave lens. Sixth lens element L6 is a biconcave lens. Seventh lens element L7 is a meniscus lens having a convex surface facing an object. Eighth lens element L8 is a meniscus lens having a concave surface facing an object. Ninth lens element L9 is a biconcave lens.

The lens elements in third lens group G3 are described. Tenth lens element L10 is a biconvex lens. Eleventh lens element L11 is a biconvex lens. Twelfth lens element L12 is a biconcave lens. Thirteenth lens element L13 is a biconcave lens. Fourteenth lens element L14 is a biconvex lens. Fifteenth lens element L15 is a biconvex lens. Sixteenth lens element L16 is a biconvex lens. Seventeenth lens element L17 is a meniscus lens having a concave surface facing an object.

The lens elements in fourth lens group G4 are described. Eighteenth lens element L18 is a meniscus lens having a convex surface facing an object and both surfaces of the lens are aspheric.

The lens elements in fifth lens group G5 are described. Nineteenth lens element L19 is a biconcave lens. Twentieth lens element L20 is a meniscus having a convex surface facing an object.

When the zoom lens system zooms from the wide-angle end to the telephoto end in imaging, first lens group G1, third lens group G3, fourth lens group G4, and fifth lens group G5 move toward an object, but second lens group G2 and image surface S do not move. In other words, each lens group moves along the optical axis when zooming so that the distance between first lens group G1 and second lens group G2 increases; second lens group G2 and third lens group G3, decreases; third lens group G3 and fourth lens group G4, decreases; and fourth lens group G4 and fifth lens group G5, decreases. Besides, as shown in FIG. 1, when the zoom lens system zooms from the wide-angle end to the telephoto end, the full-aperture diameter of aperture stop A increases.

When the zoom lens system focuses from an infinity focusing state to a proximity focusing state, fourth lens group G4 moves along the optical axis toward the image.

Here, seventh lens element L7 and eighth lens element L8, which are part of second lens group G2, move vertically to the optical axis in order to optically correct image blurring. These seventh lens element L7 and eighth lens element L8 correct the image point shift due to vibration of the entire system. That is, the elements optically correct image blurring due to hand shake or vibration for example.

Second Exemplary Embodiment

FIG. 4 illustrates a zoom lens system according to the second exemplary embodiment.

The zoom lens system is composed of first lens group G1 with positive optical power, second lens group G2 with negative optical power, third lens group G3 with positive optical power, fourth lens group G4 with negative optical power, fifth lens group G5 with positive optical power, and parallel plain plate P, in this order in the direction from an object to the image. Third lens group G3, fourth lens group G4, and fifth lens group G5 compose the subsequent lens group.

First lens group G1 is composed of first lens element L1 with negative optical power, second lens element L2 with positive optical power, and third lens element L3 with positive optical power, in this order in the direction from an object to the image.

Second lens group G2 is composed of fourth lens element L4 with positive optical power, fifth lens element L5 with negative optical power, sixth lens element L6 with negative optical power, seventh lens element L7 with positive optical power, eighth lens element L8 with positive optical power, ninth lens element L9 with negative optical power, and aperture stop A, in this order in the direction from an object to the image. Fourth lens element L4 and fifth lens element L5 are bonded together with a bonding material for example to form a cemented lens, and so are sixth lens element L6 and seventh lens element L7.

Third lens group G3 is composed of tenth lens element L10 with positive optical power, eleventh lens element L11 with positive optical power, twelfth lens element L12 with negative optical power, thirteenth lens element L13 with negative optical power, fourteenth lens element L14 with positive optical power, fifteenth lens element L15 with positive optical power, sixteenth lens element L16 with positive optical power, and seventeenth lens element L17 with negative optical power, in this order in the direction from an object to the image. Eleventh lens element L11 and twelfth lens element L12 are bonded together with a bonding material for example to form a cemented lens, and so are thirteenth lens element L13 and fourteenth lens element L14, and sixteenth lens element L16 and seventeenth lens element L17.

Fourth lens group G4 is a single lens and is composed of eighteenth lens element L18 with negative optical power.

Fifth lens group G5 is composed of nineteenth lens element L19 with negative optical power and twentieth lens element L20 with positive optical power, in this order in the direction from an object to the image. Nineteenth lens element L19 and twentieth lens element L20 are bonded together with a bonding material for example to form a cemented lens.

Each lens element is described.

The lens elements in first lens group G1 are described. First lens element L1 is a meniscus lens having a convex surface facing an object. Second lens element L2 is a meniscus lens having a convex surface facing an object. Third lens element L3 is a biconvex lens.

The lens elements in second lens group G2 are described. Fourth lens element L4 is a biconvex lens. Fifth lens element L5 is a biconcave lens. Sixth lens element L6 is a biconcave lens. Seventh lens element L7 is a meniscus lens having a convex surface facing an object. Eighth lens element L8 is a meniscus lens having a concave surface facing an object. Ninth lens element L9 is a biconcave lens.

The lens elements in third lens group G3 are described. Tenth lens element L10 is a biconvex lens. Eleventh lens element L11 is a biconvex lens. Twelfth lens element L12 is a meniscus lens having a concave surface facing an object. Thirteenth lens element L13 is a biconcave lens. Fourteenth lens element L14 is a biconvex lens. Fifteenth lens element L15 is a biconvex lens. Sixteenth lens element L16 is a biconvex lens. Seventeenth lens element L17 is a meniscus lens having a concave surface facing an object.

The lens elements in fourth lens group G4 are described. Eighteenth lens element L18 is a meniscus lens having a convex surface facing an object and both surfaces of the lens are aspheric.

The lens elements in fifth lens group G5 are described. Nineteenth lens element L19 is a biconcave lens. Twentieth lens element L20 is a meniscus having a convex surface facing an object.

When the zoom lens system zooms from the wide-angle end to the telephoto end in imaging, first lens group G1, third lens group G3, fourth lens group G4, and fifth lens group G5 move toward an object, but second lens group G2 and image surface S do not move. In other words, each lens group moves along the optical axis when zooming so that the distance between first lens group G1 and second lens group G2 increases; second lens group G2 and third lens group G3, decreases; third lens group G3 and fourth lens group G4, decreases; and fourth lens group G4 and fifth lens group G5, decreases. Besides, as shown in FIG. 4, when the zoom lens system zooms from the wide-angle end to the telephoto end, the full-aperture diameter of aperture stop A increases.

When the zoom lens system focuses from an infinity focusing state to a proximity focusing state, fourth lens group G4 moves along the optical axis toward the image.

Here, seventh lens element L7 and eighth lens element L8, which are part of second lens group G2, move vertically to the optical axis in order to optically correct image blurring. These seventh lens element L7 and eighth lens element L8 correct the image point shift due to vibration of the entire system. That is, the elements optically correct image blurring due to hand shake or vibration for example.

Third Exemplary Embodiment

FIG. 7 illustrates a zoom lens system according o the third exemplary embodiment.

The zoom lens system is composed of first lens group G1 with positive optical power, second lens group G2 with negative optical power, third lens group G3 with positive optical power, fourth lens group G4 with positive optical power, fifth lens group G5 with negative optical power, sixth lens group G6 with negative optical power, and parallel plain plate P, in this order in the direction from an object to the image. Third lens group G3, fourth lens group G4, fifth lens group G5, and sixth lens group G6 compose the subsequent lens group.

First lens group G1 is composed of first lens element L1 with negative optical power, second lens element L2 with positive optical power, and third lens element L3 with positive optical power, in this order in the direction from an object to the image. First lens element L1 and second lens element L2 are bonded together with a bonding material for example to form a cemented lens.

Second lens group G2 is composed of fourth lens element L4 with positive optical power, fifth lens element L5 with negative optical power, sixth lens element L6 with negative optical power, seventh lens element L7 with positive optical power, eighth lens element L8 with positive optical power, ninth lens element L9 with negative optical power, and aperture stop A, in this order in the direction from an object to the image. Fourth lens element L4 and fifth lens element L5 are bonded together with a bonding material for example to form a cemented lens, and so are sixth lens element L6 and seventh lens element L7.

Third lens group G3 is composed of tenth lens element L10 with positive optical power, eleventh lens element L11 with positive optical power, twelfth lens element L12 with positive optical power, and thirteenth lens element L13 with negative optical power, in this order in the direction from an object to the image. Twelfth lens element L12 and thirteenth lens element L13 are bonded together with a bonding material for example to form a cemented lens.

Fourth lens group G4 is composed of fourteenth lens element L14 with negative optical power, fifteenth lens element L15 with positive optical power, sixteenth lens element L16 with positive optical power, seventeenth lens element L17 with positive optical power, and eighteenth L18 with negative optical power, in this order in the direction from an object to the image. Seventeenth lens element L17 and eighteenth lens element L16 are bonded together with a bonding material for example to form a cemented lens.

Fifth lens group G5 is a single lens and is composed of nineteenth lens element L19 with negative optical power.

Sixth lens group G6 is composed of twentieth lens element L20 with negative optical power and twenty-first lens element L21 with positive optical power, in this order in the direction from an object to the image. Twentieth lens element L20 and twenty-first lens element L21 are bonded together with a bonding material for example to form a cemented lens.

Each lens element is described.

The lens elements in first lens group G1 are described. First lens element L1 is a meniscus lens having a convex surface facing an object. Second lens element L2 is a meniscus lens having a convex surface facing an object. Third lens element L3 is a biconvex lens.

The lens elements in second lens group G2 are described. Fourth lens element L4 is a biconvex lens. Fifth lens element L5 is a biconcave lens. Sixth lens element L6 is a biconcave lens. Seventh lens element L7 is a meniscus lens having a convex surface facing an object. Eighth lens element L8 is a meniscus lens having a concave surface facing an object. Ninth lens element L9 is a biconcave lens.

The lens elements in third lens group G3 are described. Tenth lens element L10 is a biconvex lens. Eleventh lens element L11 is a biconvex lens. Twelfth lens element L12 is a biconvex lens. Thirteenth lens element L13 is a meniscus lens having a concave surface facing an object.

The lens elements in fourth lens group G4 are described. Fourteenth lens element L14 is a biconcave lens. Fifteenth lens element L15 is a biconvex lens. Sixteenth lens element L16 is a biconvex lens. Seventeenth lens element L17 is a biconvex lens. Eighteenth lens element L18 is a meniscus lens having a concave surface facing an object.

The lens elements in fifth lens group G5 are described. Nineteenth lens element L19 is a meniscus having a convex surface facing an object and both surfaces of the lens are aspheric.

The lens elements in sixth lens group G5 are described. Twentieth lens element L20 is a biconcave lens. Twenty-first lens element L21 is a meniscus lens having a convex surface facing an object.

When the zoom lens system zooms from the wide-angle end to the telephoto end in imaging, first lens group G1, third lens group G3, fourth lens group G4, fifth lens group G5, and sixth lens group G6 move toward an object, but second lens group G2 and image surface S do not move. In other words, each lens group moves along the optical axis when zooming so that the distance between first lens group G1 and second lens group G2 increases; second lens group G2 and third lens group G3, decreases; third lens group G3 and fourth lens group G4, decreases; fourth lens group G4 and fifth lens group G5, decreases; and fifth lens group G5 and sixth lens group G6, decreases. Besides, as shown in FIG. 7, when the zoom lens system zooms from the wide-angle end to the telephoto end, the hill-aperture diameter of aperture stop A increases.

When the zoom lens system focuses from an infinity focusing state to a proximity focusing state, fifth lens group G5 moves along the optical axis toward the image.

Here, seventh lens element L7 and eighth lens element L8, which are part of second lens group G2, move vertically to the optical axis in order to optically correct image blurring. These seventh lens element L7 and eighth lens element L8 correct the image point shift due to vibration of the entire system. That is, the elements optically correct image blurring due to hand shake or vibration for example.

Other Exemplary Embodiments

Hereinbefore, the first through third embodiments are described to exemplify the technology disclosed in this patent application. The technology of the disclosure, however, is not limited to these embodiments, but is applicable to other embodiments appropriately devised through modification, substitution, addition, and omission for example.

As an example of aperture stop A positioned where it is integrated with second lens group G2, aperture stop A is between fifth lens element L5 and sixth lens element L6 in the first embodiment. However, aperture stop A may be between other two lens elements in second lens group G2. In the second and third embodiments, aperture stop A is closest to an image in second lens group G2; however, aperture stop A may be closest to an object in second lens group G2. Aperture stop A has only to be positioned where it is integrated with second lens group G2 and does not move.

Conditions and Advantages

Hereinafter, a description is made of conditions that can be satisfied by a zoom lens system according to the first through third embodiments for example. Here, some possible conditions are defined for a zoom lens system according to the first through third embodiments, and a zoom lens system that satisfies all the conditions is most effective. However, by satisfying an individual condition, a zoom lens system that provides a corresponding advantage can be achieved as well.

A zoom lens system includes a first lens group with positive optical power, a second lens group with negative optical power, and a subsequent lens group composed of at least three lens groups with positive optical power as a whole.

During zooming operation, the first lens group moves along the optical axis; the second lens group does not.

The zoom lens system has an aperture stop at a position where it is integrated with the second lens group.

Then, it is desirable for example that the zoom lens system satisfies following condition (1),

−9.0≦fG1/fG2≦−2.0   (1)

where

fG1: the focal length of the first lens group

fG2: the focal length of the second lens group.

Concrete values of the focal lengths of the first and second lens groups are shown in tables 3C, 6C, and 9C of numerical practical examples 1 through 3 (described later).

Condition (1) defines the ratio of the focal length of the first lens group to that of the second one. A ratio smaller than the lower limit of condition (1) results in a too long focal length of the first lens group, which causes a longer moving distance of the first lens group during zooming operation as well as a too large total optical length at the telephoto end. This makes it difficult to provide a compact lens barrel, imaging apparatus, and camera. Meanwhile, a ratio larger than the upper limit of condition (1) results in a too short focal length of the first lens group, which makes it difficult to correct various aberrations across the entire system, and so does to achieve a desired optical performance.

Preferably, satisfying condition (1)′ further increases the above-described effectiveness.

−5.0≦fG1/fG2≦−3.0   (1)′

Further, it is desirable for example that the zoom lens system satisfies following condition (2),

0.4≦LG2a/LG2≦0.9   (2)

where

LG2 a: the largest size of air spaces in the second lens group

LG2: the thickness of the second lens group in the optical axis direction.

Concrete values of air spaces in the second lens group are shown as surface distance d in tables 1, 4, and 7 of numerical practical examples 1 through 3 (described later). Concrete values of the thickness of the second lens group in the optical axis direction are shown as lens configuration length in tables 3C, 6C, and. 9C of numerical practical examples 1 through 3 (described later).

Condition (2) defines the ratio of the largest size of air spaces in the second lens group to the thickness of the second lens group in the optical axis direction. A ratio larger than the lower limit of condition (2) results in the largest size of air spaces in the second lens group not too small. This allows various aberrations (especially spherical aberration and coma aberration) to be adequately corrected. Meanwhile, a ratio smaller than the upper limit of condition (2) results in the largest size of air spaces in the second lens group not too large. This leads to an appropriate total optical length to provide a compact lens barrel, imaging apparatus, and camera.

Preferably, satisfying condition (2)' further increases the above-described effectiveness.

0.4≦LG2a/LG2≦0.7   (2)′

It is desirable for example that part of the second lens group moves so as to have a component in a direction perpendicular to the optical axis during image blur correction.

This decreases the lens diameter for a smaller and lighter image blur correction lens group, which allows driving the lens group with a simple driving mechanism.

A zoom lens system according to the first through third embodiments corrects blurring by moving the image blur correction lens element in a direction vertical to the optical axis. The movement method is capable of image blur correction if the lens element is moved so as to have a component in a vertical direction. For example, if the lens barrel structure is allowed to be more complicated, blurring may be corrected by rotating the image blur correction lens element so that the element has a rotation center on the optical axis.

It is desirable for example that each of the three lens elements composing the first lens group of the zoom lens system is a single lens.

This increases air spaces to enhance the design flexibility for facilitating aberration correction.

An Outline Structure of an Imaging Apparatus to which the First Embodiment has been Applied

FIG. 10 illustrates an outline structure of an imaging apparatus to which a zoom lens system according to the first embodiment has been applied. Note that a zoom lens system according to the second and third exemplary embodiments can be also applied to an imaging apparatus.

Imaging apparatus 100 is composed of housing 104, imaging element 102, and zoom lens system 101. A concrete example of imaging apparatus 100 is a digital camera.

Zoom lens system 101 includes an actuator and a lens frame for example contained in housing 104 so that first lens group G1, third lens group G3, fourth lens group G4, and fifth lens group G5 move during zooming operation.

This allows providing an imaging apparatus that is compact and has a high optical performance across the entire zoom area in spite of the large diameter.

The description is made of the example where a zoom lens system according to first embodiment has been applied to a digital camera; the zoom lens system can be also applied to a smartphones for example.

An Outline Structure of a Camera to which the First Embodiment has been Applied

FIG. 11 illustrates an outline structure of a camera to which a zoom lens system according to the first embodiment has been applied. Note that a zoom lens system according to the second and third exemplary embodiments can be also applied to a camera.

Camera 200 includes camera body 201 and interchangeable lens device 300 detachably connected to camera body 201.

Camera body 201 includes imaging element 202, monitor 203, memory (unillustrated), camera mount unit 204, and finder 205. Imaging element 202 receives an optical image formed by the zoom lens system of interchangeable lens device 300 and converts the image to an electrical image signal. Monitor 203 displays the image signal. The memory stores the image signal.

Interchangeable lens device 300 includes lens barrel 302 and lens mount unit, 304. Lens barrel 302 holds first lens group G1, second lens group G2, third lens group G3, fourth lens group G4, and fifth lens group G5. Lens mount unit 304 is connected to camera mount unit 204 of camera body 201.

Camera mount unit 204 and lens mount unit 304 function as an interface that electrically, as well as physically, connects the controller (unillustrated) inside camera body 201 with the controller (unillustrated) inside interchangeable lens device 300 to allow mutual signal exchanges.

Zoom lens system 301 is composed of the lens groups held by lens barrel 302, and parallel plain plate P of camera body 201. Zoom lens system 301 includes an actuator and a lens frame that are controlled by the controller inside interchangeable lens device 300 so that first lens group G1, third lens group G3, fourth lens group G4, and fifth lens group G5 move during zooming operation.

This allows providing a camera that is compact and has a high optical performance across the entire zoom area in spite of the large diameter.

NUMERICAL PRACTICAL EXAMPLES

Hereinafter, a description is made of some numerical practical examples from concrete zoom lens systems according to the first through third embodiments. The practical examples represent each length in the tables in the unit of mm; and each view angle, in the unit of (degree). In the practical examples, r is a curvature radius; d, a surface distance; nd, a refractive index for d-line; and vd, an Abbe number for d-line. In the practical examples, a surface with an * mark is aspheric and its shape is defined by the following expression,

$\begin{matrix} {Z = {\frac{h^{2}/r}{1 + \sqrt{1 - {\left( {1 + \kappa} \right)\left( {h/r} \right)^{2}}}} + {\sum{A_{n}h^{n}}}}} & \left\lbrack {{Expression}\mspace{14mu} 1} \right\rbrack \end{matrix}$

where

Z: the distance from a point on an aspheric surface (the height from the optical axis is h) to the tangent plane at the apex of the aspheric surface

h: the height from the optical axis

r: the curvature radius at the apex

κ: conic constant

An: n-degree aspherical coefficient.

FIGS. 2, 5, and 8 are longitudinal aberration diagrams of zoom lens systems according to practical examples 1 through 3, in an infinity focusing state.

In each longitudinal aberration diagram, part (a) shows aberration at the wide-angle end; part (b), at an intermediate position; and part (c), at the telephoto end. Each longitudinal aberration diagram shows spherical aberration (SA (nim)), astigmatism (AST (mm)), and distortion aberration (DIS (%)), in this sequence from the left. In a spherical aberration diagram, the vertical axis represents F number (shown by F in the figure). A solid line represents the characteristics of d-line; a short broken line, of F-line; a long broken line, of C-line; and an alternate long and short dashline, of g-line. In an astigmatism diagram, the vertical axis represents the image height (shown by H in the diagram). A solid line represents the characteristics of the sagittal plane (shown by s in the diagram); a broken line, of the meridional plane (shown by m in the diagram). In a distortion aberration diagram, the vertical axis represents the image height (shown by H in the diagram).

FIGS. 3, 6, and 9 are lateral aberration diagrams of zoom lens systems according to first through third embodiments, at the telephoto end.

In each lateral aberration diagram, the upper three aberration diagrams correspond to a basic state, where blurring at the telephoto end is not corrected. The lower three aberration diagrams correspond to an image blur correction state at the telephoto end in a case where the image blur correction lens group has been moved by a given amount in a direction vertical to the optical axis. In each lateral aberration diagram in a basic state, the top correspond to lateral aberration at an image point of 70% of the maximum image height; the middle, to lateral aberration at an image point on the axis; and the bottom, to lateral aberration at an image point of −70% of the maximum image height. In each lateral aberration diagram in an image blur correction state, the top correspond to lateral aberration at an image point of 70% of the maximum image height; the middle, to lateral aberration at an image point on the axis; and the bottom, to lateral aberration at an image point of −70% of the maximum image height. In each lateral aberration diagram, the horizontal axis represents the distance from the main light beam on the pupil surface. A solid line shows the characteristics of d-line; a short broken line, of F-line, a long broken line, of C-line; and an alternate long and short dashline, of g-line. In each lateral aberration diagram, a meridional plane is defined as a surface containing the optical axis of first lens group G1 and the optical axis of second lens group G2 (practical examples 1 through 3).

For the zoom lens systems of each practical example, the distance by which an image blur correction lens group moves in a direction vertical to the optical axis in an image blur correction state at the telephoto end is shown below.

Practical example 1 1.030 mm Practical example 2 0.930 mm Practical example 3 0.820 mm

At the telephoto end with a photographing distance of infinity (∞), the image eccentricity in a case where a zoom lens system is inclined by a given angle is equal to the image eccentricity in a case where the image blur correction lens group has made parallel translation in a direction vertical to the optical axis by each of the above-described values.

As is obvious from each lateral aberration diagram, the lateral aberration at an image point on the axis has a favorable symmetry. Comparisons of lateral aberration between at ±70% image point and at −70% image point in a basic state show that both have a small curve degree and an approximately equal gradient of the aberration curve, and thus the eccentric coma aberration and the eccentric astigmatism prove to be small. This means sufficient image-forming performance is achieved even in an image blur correction state. For the same image blur correction angle of a zoom lens system, a shorter focal length of the entire zoom lens system leads to a smaller distance of parallel movement required for blurring correction. Hence, sufficient image blur correction can be performed without the image-forming characteristics deteriorating for an image blur correction angle to a given angle at any zoom position.

Numerical Practical Example 1

The zoom lens system of numerical practical example 1 corresponds to the first embodiment shown in FIG. 1. Table 1 shows surface data of the zoom lens system of numerical practical example 1. Table 2 shows aspheric data. Tables 3A through 3D show various data in an infinity focusing state.

(Surface Data)

TABLE 1 Surface No. r d nd vd Object surface ∞  1 100.06160 2.20000 1.80610 33.3  2 67.50200 0.50000  3 67.19710 8.23000 1.49700 81.6  4 894.41750 0.20000  5 187.16930 3.60430 1.43700 95.0  6 10935.15130 variable  7 66.68480 3.74160 1.78472 25.7  8 −239.69110 0.01000 1.56732 42.8  9 −239.69110 1.30000 1.54814 45.8 10 53.01340 19.18400 11 (aperture) ∞ 1.80000 12 −269.01920 0.80000 1.84666 23.8 13 49.41850 0.01000 1.56732 42.8 14 49.41850 2.20560 1.51742 52.1 15 817.66370 2.96900 16 −45.56550 1.75350 1.80610 33.3 17 −29.41180 0.01000 1.56732 42.8 18 −29.41180 0.80000 1.51823 59.0 19 82.23550 variable 20 37.08220 5.02730 1.49700 81.6 21 −47.16140 0.40000 22 61.05640 4.75800 1.56732 42.8 23 −30.54900 0.01000 1.56732 42.8 24 −30.54900 0.80000 1.90366 31.3 25 1854.08490 2.00000 26 −55.99840 0.80000 1.83481 42.7 27 21.46700 0.01000 1.56732 42.8 28 21.46700 5.09020 1.69895 30.0 29 −121.98450 23.14160 30 151.96250 4.37150 1.51742 52.1 31 −30.71290 0.20000 32 48.52190 4.95390 1.51823 59.0 33 −30.62320 0.01000 1.56732 42.8 34 −30.62320 0.80000 1.90366 31.3 35 −172.12560 variable 36* 63.90120 0.80000 1.49710 81.6 37* 18.36410 variable 38 −46.46240 0.80000 1.61800 63.4 39 18.78150 0.01000 1.56732 42.8 40 18.78150 3.59480 1.67270 32.2 41 1456.48430 variable 42 ∞ 4.20000 1.51680 64.2 43 ∞ BF Image surface ∞

(Aspheric Surface Data)

TABLE 2 Thirty-sixth surface κ = 0.00000E+00, A4 = −8.12688E−06, A6 = 1.14467E−07, A8 = 7.22357E−10, A10 = −1.59277E−11 Thirty-seventh surface κ = 0.00000E+00, A4 = −1.07383E−05, A6 = 8.31780E−08, A8 = 1.93598E−09, A10 = −2.96510E−11

(Various Data in Infinity Focusing State)

TABLE 3A Intermediate Wide-angle end position Telephoto end Focal length 103.0054 199.9222 388.0283 Zoom ratio 1.00000 1.94089 3.76707 F number 4.12033 5.17059 6.49059 View angle 5.8880 3.0455 1.5774 Image height 10.8150 10.8150 10.8150 Total lens length 184.0949 231.9725 259.6874 BF 1.09447 0.97213 1.05519 d6 1.0000 49.0000 76.6317 d19 19.4767 14.3942 3.8806 d35 17.5845 10.9731 2.0000 d37 22.1439 21.3971 20.0000 d41 11.7000 24.1407 45.0246 Entrance pupil 43.1468 145.5110 259.6189 position Exit pupil position −72.8754 −79.4276 −93.3378 Front principal 2.7138 −151.6939 −947.4505 point Rear principal 81.0894 32.0504 −128.3410 point

TABLE 3B Data of Single Lens Lens elements First surface Focal length L1 1 −265.3475 L2 3 145.7080 L3 5 435.7193 L4 7 66.8418 L5 9 −79.0741 L6 12 −49.2536 L7 14 101.5538 L8 16 98.1635 L9 18 −41.7013 L10 20 42.6140 L11 22 36.5782 L12 24 −33.2512 L13 26 −18.5019 L14 28 26.5040 L15 30 49.7843 L16 32 37.0187 L17 34 −41.3328 L18 36 −52.1444 L19 38 −21.5415 L20 40 28.2559

TABLE 3C Data of Zoom Lens Groups Lens Front Rear Lens First configuration principal principal groups surface Focal length length point point G1 1 190.14254 14.73430 2.12129 6.85443 G2 7 −50.06006 34.58370 36.23257 36.30302 G3 20 44.14465 52.37250 38.01837 26.12802 G4 36 −52.14441 0.80000 0.75426 1.01676 G5 38 −92.21687 4.40480 −0.02337 1.73399

TABLE 3D Magnification of a zoom lens groups Lens First Wide-angle Intermediate Telephoto groups surface end position end G1 1 0.00000 0.00000 0.00000 G2 7 −0.52711 −1.06579 −2.58864 G3 20 −0.50120 −0.40145 −0.25127 G4 36 1.71202 1.84585 2.01283 G5 38 1.19773 1.33131 1.55868

Numerical Practical Example 2

The zoom lens system of numerical practical example 2 corresponds to the second embodiment shown in FIG. 4. Table 4 shows surface data of the zoom lens system of numerical practical example 2. Table 5 shows aspheric data. Tables 6A through 6D show various data in an infinity focusing state.

(Surface Data)

TABLE 4 Surface No. r d nd vd Object surface ∞  1 109.12370 2.20000 1.80610 33.3  2 67.44820 0.50000  3 67.10640 6.85210 1.49700 81.6  4 293.87390 0.20000  5 140.75750 5.31170 1.49700 81.6  6 −525.23090 variable  7 45.83450 5.30480 1.80518 25.5  8 −286.94940 0.01000 1.56732 42.8  9 −286.94940 0.80000 1.62004 36.3 10 42.47790 17.52850 11 −250.42960 0.80000 1.84666 23.8 12 37.69820 0.01000 1.56732 42.8 13 37.69820 2.48050 1.56732 42.8 14 137.26890 9.30790 15 −42.05600 1.50080 1.80518 25.5 16 −30.13390 0.20000 17 −32.25810 0.80000 1.56883 56.0 18 90.51700 1.70590 19 (aperture) ∞ variable 20 38.09930 4.78770 1.49700 81.6 21 −53.18270 0.40000 22 53.78720 5.03010 1.54814 45.8 23 −30.89420 0.01000 1.56732 42.8 24 −30.89420 0.80000 1.90366 31.3 25 −738.24690 2.39810 26 −63.65240 0.80000 1.83481 42.7 27 22.26330 0.01000 1.56732 42.8 28 22.26330 4.99370 1.69895 30.0 29 −128.84210 16.61420 30 120.69590 4.36650 1.51742 52.1 31 −30.62540 0.20000 32 38.94020 4.94570 1.51823 59.0 33 −32.85770 0.01000 1.56732 42.8 34 −32.85770 0.80000 1.90366 31.3 35 −865.48620 variable 36* 88.83300 0.80000 1.49710 81.6 37* 20.44880 variable 38 −84.84820 0.80000 1.80420 46.5 39 25.96370 0.01000 1.56732 42.8 40 25.96370 2.92040 1.84666 23.8 41 245.50180 variable 42 ∞ 4.20000 1.51680 64.2 43 ∞ BF Image surface ∞

(Aspheric Surface Data)

TABLE 5 Thirty-sixth surface κ = 0.00000E+00, A4 = 4.50634E−05, A6 = −5.17727E−07, A8 = 2.75710E−09, A10 = −7.82291E−12 Thirty-seventh surface κ = 0.00000E+00, A4 = 4.71906E−05, A6 = −4.64808E−07, A8 = 1.74656E−09, A10 = −4.65745E−12

(Various Data in Infinity Focusing State)

TABLE 6A Intermediate Wide-angle end position Telephoto end Focal length 103.0057 199.9199 388.0146 Zoom ratio 1.00000 1.94086 3.76692 F number 4.12039 5.17066 6.49053 View angle 5.9001 3.0438 1.5744 Image height 10.8150 10.8150 10.8150 Total lens length 184.0715 224.0498 250.0984 BF 1.07147 0.94968 1.10085 d6 1.0000 41.1000 66.9974 d19 18.8597 12.4399 1.8000 d35 13.4231 9.3753 2.0000 d37 27.6086 20.6617 15.9138 d41 11.7000 29.1146 51.8778 Entrance pupil 73.7400 187.2512 338.7995 position Exit pupil position −62.6815 −74.2537 −90.1584 Front principal 10.3195 −144.2941 −922.9395 point Rear principal 81.0658 24.1299 −137.9161 point

TABLE 6B Data of Single Lens Lens elements First surface Focal length L1 1 −224.3751 L2 3 173.2428 L3 5 223.9508 L4 7 49.4357 L5 9 −59.6191 L6 11 −38.6507 L7 13 90.7893 L8 15 125.0005 L9 17 −41.7111 L10 20 45.4545 L11 22 36.5685 L12 24 −35.7003 L13 26 −19.6747 L14 28 27.5338 L15 30 47.6788 L16 32 35.2155 L17 34 −37.8129 L18 36 −53.6451 L19 38 −24.6413 L20 40 34.0847

TABLE 6C Data of Zoom Lens groups Lens Front Rear Lens First configuration principal principal groups surface Focal length length point point G1 1 178.17838 15.06380 3.56898 8.47678 G2 7 −41.90178 40.44840 42.01295 39.69068 G3 20 39.34189 46.16600 27.72846 22.52163 G4 36 −53.64513 0.80000 0.69686 0.96041 G5 38 −88.17738 3.73040 0.54730 2.25684

TABLE 6D Magnification of Zoom Lens Groups Intermediate Telephoto Lens groups First surface Wide-angle end position end G1 1 0.00000 0.00000 0.00000 G2 7 −0.48343 −0.89963 −2.02627 G3 20 −0.56073 −0.48461 −0.33411 G4 36 1.78772 1.85276 1.95074 G5 38 1.19295 1.38907 1.64893

Numerical Practical Example 3

The zoom lens system of numerical practical example 3 corresponds to the third embodiment shown in. FIG. 7. Table 7 shows surface data of the zoom t lens system of numerical practical example 3. Table 8 shows aspheric data. Tables 9A through 9D show various data in an infinity focusing state.

(Surface Data)

TABLE 7 Surface No. r d nd vd Object surface ∞  1 111.52190 2.20000 1.80610 33.3  2 61.02740 0.01000 1.56732 42.8  3 61.02740 5.14960 1.59282 68.6  4 172.27030 0.20000  5 97.10050 5.16900 1.49700 81.6  6 −935.19380 variable  7 45.33960 4.84300 1.80518 25.5  8 −159.13700 0.01000 1.56732 42.8  9 −159.13700 0.80000 1.62004 36.3 10 54.00980 15.19130 11 −692.52560 0.80000 1.84666 23.8 12 26.12640 0.01000 1.56732 42.8 13 26.12640 2.14510 1.58144 40.9 14 64.76980 2.31760 15 −50.90710 1.31380 1.80518 25.5 16 −35.21860 0.20000 17 −40.43450 0.80000 1.74330 49.2 18 110.84260 1.57550 19 (aperture) ∞ variable 20 41.85100 3.98580 1.49700 81.6 21 −56.27000 0.20000 22 154.97430 1.68040 1.49700 81.6 23 −179.97080 0.20000 24 115.35270 3.72610 1.54814 45.8 25 −31.51190 0.01000 1.56732 42.8 26 −31.51190 0.80000 1.90366 31.3 27 −100.04270 variable 28 −32.26500 0.80000 1.83481 42.7 29 28.84920 0.01000 1.56732 42.8 30 28.84920 3.88700 1.69895 30.0 31 −73.17790 11.44280 32 518.40640 4.03860 1.51742 52.1 33 −26.67810 0.20000 34 50.72660 4.44870 1.51823 59.0 35 −26.76570 0.01000 1.56732 42.8 36 −26.76570 0.80000 1.90366 31.3 37 −79.44420 variable 38* 89.20270 0.80000 1.49710 81.6 39* 20.91380 variable 40 −85.01730 0.80000 1.80420 46.5 41 22.27810 0.01000 1.56732 42.8 42 22.27810 2.65620 1.84666 23.8 43 145.83210 variable 44 ∞ 4.20000 1.51680 64.2 45 ∞ BF Image surface ∞

(Aspheric Surface Data)

TABLE 8 Thirty-eighth surface κ = 0.00000E+00, A4 = 5.53040E−05, A6 = −8.74771E−07, A8 = 8.91726E−09, A10 = −4.71040E−11 Thirty-ninth surface κ = 0.00000E+00, A4 = 6.02177E−05, A6 = −8.76790E−07, A8 = 9.24437E−09, A10 = −5.55747E−11

Various Data in Infinity Focusing State

TABLE 9A Intermediate Wide-angle end position Telephoto end Focal length 103.0203 187.0117 339.5180 Zoom ratio 1.00000 1.81529 3.29564 F number 4.12082 5.16344 6.49079 View angle 5.8937 3.2537 1.7988 Image height 10.8150 10.8150 10.8150 Total lens length 160.0266 190.9791 220.9254 BF 1.02411 0.97660 0.97443 d6 1.0000 32.0000 61.9484 d19 16.5852 9.0733 1.8000 d27 4.7810 5.7197 2.6664 d37 11.2758 8.8595 1.9998 d39 26.2200 17.1291 15.0002 d43 11.7000 29.7804 49.0957 Entrance pupil 55.0606 125.9696 256.4324 position Exit pupil position −58.0366 −69.7179 −83.7243 Front principal −21.6185 −181.7303 −765.0204 point Rear principal 57.0063 3.9674 −118.5926 point

TABLE 9B Data of Single Lens Lens elements First surface Focal length L1 1 −170.5221 L2 3 156.7189 L3 5 177.2916 L4 7 44.2919 L5 9 −64.9414 L6 11 −29.7211 L7 13 73.8070 L8 15 136.8198 L9 17 −39.7689 L10 20 48.9512 L11 22 167.8255 L12 24 45.5630 L13 26 −51.1898 L14 28 −18.1366 L15 30 30.0755 L16 32 49.1606 L17 34 34.4848 L18 36 −44.9930 L19 38 −55.1705 L20 40 −21.8776 L21 42 30.7542

TABLE 9C Data of Zoom Lens Groups Lens Front Rear Lens First configuration principal principal groups surface Focal length length point point G1 1 169.03373 12.72860 1.45372 6.01125 G2 7 −41.90027 30.00630 37.55049 34.12547 G3 20 35.04890 10.60230 1.84597 5.35215 G4 28 57.30903 25.63710 27.27132 42.77534 G5 38 −55.17052 0.80000 0.70074 0.96429 G6 40 −74.41918 3.46620 0.74636 2.33702

TABLE 9D Magnification of Zoom Lens Groups Lens First Wide-angle Intermediate Telephoto groups surface end position end G1 1 0.00000 0.00000 0.00000 G2 7 −0.51182 −0.82374 −2.00315 G3 20 −0.82258 −0.72766 −0.38809 G4 28 0.68318 0.71978 0.80977 G5 38 1.73208 1.74960 1.84945 G6 40 1.22336 1.46568 1.72519

Corresponding Values of Conditions

Following table 10 shows corresponding values of conditions rounded off to the second decimal place.

TABLE 10 Numerical Numerical Numerical practical practical practical example 1 example 2 example 3 Condition (1) −3.80 −4.25 −4.03 Condition (2) 0.61 0.45 0.53

INDUSTRIAL APPLICABILITY

A zoom lens system according to the present disclosure is applicable to a digital still camera, an interchangeable lens digital camera, a digital video camera, a camera unit of a mobile phone, a camera unit of a personal digital assistance (PDA), a monitoring camera in a monitoring system, a web camera, and a vehicle-mounted camera, for example, and is ideal especially for a photographing optical system requiring high image quality such as a digital still camera system and a digital video camera system. 

What is claimed is:
 1. A zoom lens system,in order from an object side to an image side, comprising: a first lens group with positive optical power; a second lens group with negative optical power; and a subsequent lens group with positive optical power as a whole including at least three lens groups, wherein during zooming operation, the first lens group moves along an optical axis, and the second lens group does not move along the optical axis, and wherein the second lens group has an aperture stop and satisfies condition (1) below, −9.0≦fG1/fG2≦−2.0   (1) where fG1 is a focal length of the first lens group, and fG2 is a focal length of the second lens group.
 2. The zoom lens system of claim 1, wherein the zoom lens system satisfies condition (2) below, 0.4≦LG2a/LG2≦0.9   (2) where LG2 a is a largest size of air spaces inside the second lens group, and LG2 is a thickness of the second lens group in a direction of the optical axis.
 3. The zoom lens system of claim 1, wherein some lens element of the second lens group move so as to have a component vertical to the optical axis in image blur correction.
 4. The zoom lens system of claim 1, wherein the first lens group is composed of three single lenses.
 5. The zoom lens system of claim 1, wherein the subsequent lens group is composed of: a third lens group with positive optical power; a fourth lens group with negative optical power; and a fifth lens group with negative optical power.
 6. The zoom lens system of claim 1, wherein the subsequent lens group is composed of: a third lens group with positive optical power; a fourth lens group with positive optical power; a fifth lens group with negative optical power; and a sixth lens group with negative optical power.
 7. An imaging apparatus comprising: a zoom lens system that forms an optical image of an object; and an imaging element that converts the optical image formed by the zoom lens system to an electrical image signal, wherein the zoom lens system, in order from an object side to an image side, includes: a first lens group with positive optical power; a second lens group with negative optical power; and a subsequent lens group with positive optical power as a whole including at least three lens groups, and wherein, during zooming operation, the first lens group moves along an optical axis, and the second lens group does not move along the optical axis, and wherein the second lens group has an aperture stop and satisfies condition (1) below, −9.0≦fG1/fG2≦−2.0   (1) where fG1 is a focal length of the first lens group, and fG2 is a focal length of the second lens group.
 8. A camera comprising: a zoom lens system that forms an optical image of an object; and an imaging element that converts the optical image formed by the zoom lens system to an electrical image signal, wherein the zoom lens system, in order from an object side to an image side, includes: a first lens group with positive optical power; a second lens group with negative optical power; and a subsequent lens group with positive optical power as a whole including; at least three lens groups, and wherein, during zooming operation, the first lens group moves along an optical axis, and the second lens group does not move along the optical axis, wherein the second lens group has an aperture stop and satisfies condition (1) below, −9.0≦fG1/fG2≦−2.0   (1) where fG1 is a focal length of the first lens group, and fG2 is a focal length of the second lens group, and wherein the camera performs at least one of displaying and storing the image signal converted by the imaging element. 